Production of photographs in blueblack tones



Patented Apr. 11, 1939 UNITED STATES PATENT OFFICE PRODUCTION OF PHOTOGRAPHS IN BLUE- BLACK TUNES Hans Fricke, Wolfen, Kreis Bitterfeld, and Emil Joachim Birr, Bitterfeld, Germany, assignors to Agfa Ansco Corporation, Binghamton, N. Y., a corporation of New York No Drawing. Application June 13, 1938, Serial No. 213,448. In Germany June 19, 1937 6 Claims,

- Our present invention relates to the production of photographs in blue-black tones.

Various agents for the production of photographs from silver chloride and silver chlorideand formaldehyde has been proposed, but this has the drawback that with a long development it causes fogging. l

It is one object of our invention to provide a process of producing photographs in blue-black tones which overcomes the disadvantages above cited.

Another object of the invention is the provision of a process of producing su'ch blue-black pictures in which a dialkylated 3-alkyl-2-thiohydantoin is present during development.

Yet another object is to provide a process for theproduction of such pictures by using a dialkylated 3-alkylene-2-thiohydantoin.

Further objects and advantages of the invention are set forth in the following disclosure.

The novel agent may be added to the developing bath or introduced before the development, for example as an addition to the emulsion or to the photographic material. The incorporation of the agent in the emulsion may be carried out by adding it either to the raw material or to the emulsion in any desired stage in its manufacture or by bathing the finished emulsion layer before exposure in a solution of the agent. The agent may, however, be incorporated in the emulsion support, the subbing layer, sub-layer, backing layer or protecting layer, the barytage, the size for the paper on which the emulsions may be coated or the paper pulp. The quantity of material to be added is in all cases advantageously ascertained by preliminary experiment, whereby the optimum quantity can readily be .found. The decisive condition for effectiveness of the agents is that they shall be present during development; it being immaterial whether they are already present before the development or whether they reach the developer from the photographic material or come in contact therewith in the emulsion layer only during the development.

The effect of the dialkylated thiohydantoins was not to be foreseen since it is known that unoper ready for use.

substituted thiohydantoins present in the developer cause fogging.

The invention is illustrated by the following examples.

Example 1 T a developer for, developing silver bromide paper there-is added 0.075 gram of 3.5.5' -trimeth yl-2-thiohydantoin per liter of developer. 3.5.5 trimethyl-z-thiohydantoin is obtained as follows: 11.8 grams of -amino-in'sobutyric acid are neutralized by a solution of potassium hydroxide of 50 per cent strength and heated with an alcoholic solution of 8 grams of methyl mustard oil. The alcohol is then evaporated and the whole heated with hydrochloric acid for a short time. The product thus obtained is recrystallized from water.

Example 2 Example 3 To a developer for developing a picture copied on silver bromide is added 0.1 gram of 3-ethyl- 5.5-dimethyl 2-thiohydantoin per liter of devel- 3-ethy1-5.5-dimethyl-2- thiohydantoin is produced analogous to the manmustard oil there is used ethyl mustard oil.

Example 4 To a positive emulsion ready for pouring is added an. aqueous solution of 3-a11yl-5.5-di- Example 5 To a'positive emulsion ready for pouring is added an aqueous solution of 3-amylene-5.5-dimethyl-Z-thiohydantoin which is obtained analogous to the method described in Example 1;

instead of methyl mustard oil it is caused amyl- 45 ene mustard oil to react. We claim:

'ner described in Example 1. Instead of methyl methyI-ZrthiohydantOin which is obtained anal- 1. In a process for producing developed silver pictures in blue-black-tones from silver halide emulsions,- the improvement which comprises developing said silver halide emulsions in the presence of a member selected from the group con-' sisting of diallwlated 3-alkyl-2-thiohydantoins and dialkylated 3-alkylene-Z-thiohydantoins.

2. In a process for producing developed silver 5 pictures in blue-black tones from silver halide emulsions, the improvement which comprises developing said silver'halide emulsions in the presence of 3.5.5-thimethyl-2-thiohydantoin.

3. In a process for producing developed silver pictures in blue-black tones from silver halide emulsions, the improvement which comprises developing said silver halide emulsions in the presence of 3-ethyl-5-5-dimethyl-2-thiohydantoin.

4. In a process for producing developed silver pictures in blue-black tones from silver halide emulsions, the improvement which comprises developing said silver halide emulsions in the presence of 3-allyl-5.5'-dimethyl*2-thiohydantoin.

5. A photographic material comprising a silver halide emulsion layer containing a member selected from the group consisting of diallwlated 3-alkyl-2-thiohydantoins and dialkylated 3-allyl-2-thiohydantoins;

6. A photographic developer comprising developing agents and a. member selected from the group consisting of dialkylated 3-alkyl-2-thiohydantoins 'and dialkylated 2-allyl-2-thiohydantoins.

HANS FRICKE.

EMIL JOACI-IEM BIRR. 

